Formation enhancement of the C54-TiSi₂ by a multi-cycle pre-cooling treatment

This work investigated effects of different processing methods on the transformation of the C49-TiSi₂ phase to the C54-TiSi₂ phase in 20nm IMP Ti/Si thin films. A multi-cycle pre-cooling treatment was added to the titanium silicidation process sequence before the rapid thermal annealing (RTA) step. Compared with the conventional process, this new processing method was found to enhance formation of the low-resistivity C54-TiSi₂ phase. The extent to which the C49 transformed to the C54 phase at 720°C was observed to increase with the number of the pre-cooling cycle. The kinetic mechanisms of the C49 to C54 phase transformation were adopted to explain the experimental results. It is considered that defects at the Si/Ti interface caused by the thermal mismatch between these two layers during the pre-cooling treatment contributed to the increase in the C49 nucleation sites. This supplied more C49 grain boundaries and triple junction sites at which the C54 phase could nucleate. This discovery has a potential of reducing the complexity and cost associated with forming the low-resistivity C54 phase on sub-micron structures.